Xuanzhen Cen
57207688967
Publications - 10
Running-Induced Fatigue Exacerbates Anteromedial ACL Bundle Stress in Females with Genu Valgum: A Biomechanical Comparison with Healthy Controls
Publication Name: Sensors
Publication Date: 2025-08-01
Volume: 25
Issue: 15
Page Range: Unknown
Description:
Genu valgum (GV) is a common lower limb deformity that may increase the risk of anterior cruciate ligament (ACL) injury. This study used OpenSim musculoskeletal modeling and kinematic analysis to investigate the mechanical responses of the ACL under fatigue in females with GV. Eight females with GV and eight healthy controls completed a running-induced fatigue protocol. Lower limb kinematic and kinetic data were collected and used to simulate stress and strain in the anteromedial ACL (A–ACL) and posterolateral ACL (P–ACL) bundles, as well as peak joint angles and knee joint stiffness. The results showed a significant interaction effect between group and fatigue condition on A–ACL stress. In the GV group, A–ACL stress was significantly higher than in the healthy group both before and after fatigue (p < 0.001) and further increased following fatigue (p < 0.001). In the pre-fatigued state, A–ACL strain was significantly higher during the late stance phase in the GV group (p = 0.036), while P–ACL strain significantly decreased post-fatigue (p = 0.005). Additionally, post-fatigue peak hip extension and knee flexion angles, as well as pre-fatigue knee abduction angles, showed significant differences between groups. Fatigue also led to substantial changes in knee flexion, adduction, abduction, and hip/knee external rotation angles within the GV group. Notably, knee joint stiffness in this group was significantly lower than in controls and decreased further post-fatigue. These findings suggest that the structural characteristics of GV, combined with exercise-induced fatigue, exacerbate A–ACL loading and compromise knee joint stability, indicating a higher risk of ACL injury in fatigued females with GV.
Open Access: Yes
DOI: 10.3390/s25154814
The Effects of Skill Level on Lower-Limb Injury Risk During the Serve Landing Phase in Male Tennis Players
Publication Name: Applied Sciences Switzerland
Publication Date: 2025-03-01
Volume: 15
Issue: 5
Page Range: Unknown
Description:
The kinematic and kinetic performance of tennis players differs across skill levels, with joint range of motion (ROM), moments, and stiffness being strongly linked to injury risk. Focusing on the biomechanical characteristics of lower-limb joints throughout the landing stage, especially among athletes of different skill levels, aids in understanding the link between injury risk and performance level. This study recruited 15 male campus tennis enthusiasts and 15 male professional tennis players. The kinematic and kinetic differences between amateur and professional players during the landing phase of the tennis serve were analyzed using SPM1D 0.4.11 and SPSS 27.0.1, with independent-sample t-tests applied in both cases. Throughout the tennis serve’s landing stage, the professional group exhibited significantly greater sagittal plane hip-joint stiffness (p < 0.001), horizontal plane moment (59~91%; p = 0.036), and a significantly higher peak moment (p = 0.029) in comparison with the amateur group. For the knee joint, the professional group exhibited significantly larger ROM in flexion–extension (0~82%; p = 0.003); along with greater ROM (0~29%; p = 0.042), moment (12~100%; p < 0.001), peak moment (p < 0.001) in adduction-abduction; and internal–external rotational moments (19~100%; p < 0.001) were markedly higher. The professional group showed significantly higher ankle joint ROM (p < 0.001) and moments (6~74%; p = 0.004) in the sagittal plane, as well as greater horizontal-plane ROM (27~67%; p = 0.041) and peak moments (p < 0.001). Compared with amateur tennis players, professional tennis players exhibit greater ROM, joint moments, and stiffness in specific planes, potentially increasing their risk of injury during the landing phase.
Open Access: Yes
DOI: 10.3390/app15052681
Integrating footwear features into fatigue prediction models for marathon runners: A hybrid CNN-LSTM approach
Publication Name: Proceedings of the Institution of Mechanical Engineers Part P Journal of Sports Engineering and Technology
Publication Date: 2025-01-01
Volume: Unknown
Issue: Unknown
Page Range: Unknown
Description:
Footwear design, especially the curvature of carbon plates, may influence fatigue perception, but few studies have integrated footwear features into fatigue prediction models. This study aimed to develop a hybrid CNN-LSTM model to predict runners’ fatigue states and evaluate the impact of footwear characteristics on fatigue perception. Twelve male marathon runners (age = 21.8 ± 1.3 years; body mass = 59.1 ± 4.1 kg; height = 168.9 ± 2.2 cm; and weekly mileage = 68.8 ± 5.5 km) participated. They wore two types of carbon-plated shoes (flat plate, FP, and curved plate (CP)) and ran at a steady pace (Borg score 13) until a Borg score of 16 or 85% of maximum heart rate was reached for 2 min. EMG signals and physiological data were collected during treadmill running. A hybrid CNN-LSTM model was trained with and without footwear features to predict fatigue states. The model with footwear features achieved 85% accuracy, compared to 69% without. Curved carbon plate (CP) shoes delayed semi-fatigue onset, indicating better initial support, but the time to full fatigue was similar for both shoe types. The CNN-LSTM model effectively predicted fatigue states, with significant improvement when footwear features were included. Footwear design, particularly carbon plate curvature, influenced fatigue perception.
Open Access: Yes
Control Deficits and Compensatory Mechanisms in Individuals with Chronic Ankle Instability During Dual-Task Stair-to-Ground Transition
Publication Name: Bioengineering
Publication Date: 2025-10-01
Volume: 12
Issue: 10
Page Range: Unknown
Description:
(1) Background: Chronic ankle instability (CAI), a common outcome of ankle sprains, involves recurrent sprains, balance deficits, and gait impairments linked to both peripheral and central neuromuscular dysfunction. Dual-task (DT) demands further aggravate postural control, especially during stair descent, a major source of fall-related injuries. Yet the biomechanical mechanisms of stair-to-ground transition in CAI under dual-task conditions remain poorly understood. (2) Methods: Sixty individuals with CAI and age- and sex-matched controls performed stair-to-ground transitions under single- and dual-task conditions. Spatiotemporal gait parameters, center of pressure (COP) metrics, ankle inversion angle, and relative joint work contributions (Ankle%, Knee%, Hip%) were obtained using 3D motion capture, a force plate, and musculoskeletal modeling. Correlation and regression analyses assessed the relationships between ankle contributions, postural stability, and proximal joint compensations. (3) Results: Compared with the controls, the CAI group demonstrated marked control deficits during the single task (ST), characterized by reduced gait speed, increased step width, elevated mediolateral COP root mean square (COP-ml RMS), and abnormal ankle inversion and joint kinematics; these impairments were exacerbated under DT conditions. Individuals with CAI exhibited a significantly reduced ankle plantarflexion moment and energy contribution (Ankle%), accompanied by compensatory increases in knee and hip contributions. Regression analyses indicated that Ankle% significantly predicted COP-ml RMS and gait speed (GS), highlighting the pivotal role of ankle function in maintaining dynamic stability. Furthermore, CAI participants adopted a “posture-first” strategy under DT, with concurrent deterioration in gait and cognitive performance, reflecting strong reliance on attentional resources. (4) Conclusions: CAI involves global control deficits, including distal insufficiency, proximal compensation, and an inefficient energy distribution, which intensify under dual-task conditions. As the ankle is central to lower-limb kinetics, its dysfunction induces widespread instability. Rehabilitation should therefore target coordinated lower-limb training and progressive dual-task integration to improve motor control and dynamic stability.
Open Access: Yes
Advances and future directions of foetal finite element modelling in childbirth: from biomechanical interactions to clinical implications
Publication Name: International Journal of Biomedical Engineering and Technology
Publication Date: 2025-01-01
Volume: 49
Issue: 2
Page Range: 139-168
Description:
This review aims to summarise the applications of finite element modelling used in labour mechanics and explore their clinical relevance in optimising labour management and intervention strategies. A systematic literature search was performed in accordance with the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines across the PubMed, IEEE Xplore, Web of Science and Elsevier ScienceDirect databases. Selected 13 studies were evaluated based on the methodological quality assessment of single-subject finite element analysis (MQSSFE). The review highlights the widespread use of whole-body foetal finite element models in childbirth simulations. Key factors in childbirth biomechanics include uterine contraction intensity, abdominal muscle forces, pelvic floor function, foetal head flexion, tissue properties, and descent trajectory. Finite element modelling offers key insights but faces challenges in accuracy, personalised anatomy, and clinical application. Advances in computational biomechanics, imaging validation, and patient-specific simulations will improve childbirth understanding, risk assessment and labour management.
Open Access: Yes
The impact of cognitive load on lower limb biomechanics during the take-off phase before service in tennis players of different levels
Publication Name: Journal of Sports Sciences
Publication Date: 2026-01-01
Volume: 44
Issue: 7
Page Range: 896-906
Description:
This study examines the impact of cognitive load (CL) on lower limb biomechanics during the take-off preparation phase of the platform serve in tennis players of varying skill levels. Fifteen elite and fifteen amateur tennis players performed platform serves before and after completing a 30-minute Stroop task designed to induce CL. Key biomechanical parameters, including joint range of motion (ROM), joint moments, centre of mass (COM) displacement, and ground reaction force (GRF), were assessed using both kinematic and kinetic analysis. After CL, the biomechanical performance of amateur athletes significantly decreased compared to elite athletes. Specifically, amateur athletes showed a 14.19° lower ankle joint range of motion in the sagittal plane (p < 0.001), a 0.04-meter lower COM displacement in the frontal plane (p = 0.017), and a 0.15 Nm/BW lower knee extension moment (p < 0.001). CL adversely affects the lower limb biomechanics of amateur players more than elite players, with elite players demonstrating greater stability. These findings suggest that elite players have developed more efficient motor control mechanisms through extensive training. Tailored training interventions that account for different skill levels could enhance performance stability and mitigate the risk of injury.
Open Access: Yes
Foot Progression Angle Modulates Three-Dimensional Lower-Limb Biomechanics in Flexible Flatfoot: Kinematic–Kinetic Patterns and Clinical Implications
Publication Name: Journal of Foot and Ankle Research
Publication Date: 2026-03-01
Volume: 19
Issue: 1
Page Range: Unknown
Description:
Introduction: Foot progression angle affects gait and lowerlimb alignment. Altered angles may increase knee and ankle loading and produce tissue loading patterns previously linked to musculoskeletal injury. This study investigates how different foot progression angles modify knee and ankle biomechanics in young adults with flexible flatfoot. Methods: 28 participants (aged 18–35 years) with flexible flatfoot completed gait trials under three foot progression angle conditions. Kinematic and kinetic variables were analyzed using one-dimensional statistical parametric mapping. A 1D convolutional neural network was applied to classify progression angle patterns based on flexible flatfoot severity and gait biomechanics. Results: Decreasing foot progression angle reduced the ankle eversion/inversion range and knee abduction and external rotation (p < 0.05). Increasing foot progression angle lowered early stance ankle plantarflexion and increased knee abduction/external rotation (p < 0.05). Kinetically, a smaller foot progression angle reduced peak ankle plantarflexion moment and knee extension moment but increased the first peak of the knee adduction moment and rotational moment fluctuations (p < 0.05). A larger foot progression angle reduced rotational fluctuations and terminal stance knee extension moment (p < 0.05). The convolutional neural network model was most accurate for moderate flexible flatfoot cases, and ankle coronal and knee transverse biomechanics showed the strongest discriminative power. Conclusion: Modifying the foot progression angle can meaningfully alter knee and ankle loading in young adults with flexible flatfoot. Neutral or mild toe-in angles may help mitigate excessive eversion and rotational stress, suggesting a simple noninvasive adjustment that clinicians can incorporate during gait retraining or orthotic prescription. Because biomechanical responses vary across individuals, FPA modification may be the most effective when tailored to patient-specific gait characteristics. In addition, deep-learning-based gait classification shows promise for supporting personalized monitoring and guiding clinical decision-making during rehabilitation.
Open Access: Yes
DOI: 10.1002/jfa2.70126
Foot Progression Angle Modulates Knee Loading During Walking in Individuals with Flexible Flatfoot
Publication Name: Annals of Biomedical Engineering
Publication Date: 2026-01-01
Volume: Unknown
Issue: Unknown
Page Range: Unknown
Description:
Purpose: This study evaluated tibiofemoral loading and medial meniscal stress distribution in individuals with flexible flatfoot (FFF) during walking under different foot progression angle (FPA) conditions. Methods: This study analyzed the gait of 28 FFF patients (16 males, 12 females) under three FPA conditions (neutral, toe-in, toe-out). Kinematic (Vicon) and kinetic (Kistler) data were used to estimate tibiofemoral forces in OpenSim. Subsequently, joint angles and muscle forces at peak tibiofemoral forces were used to drive a finite element (FE) model of the knee, enabling the comparison of meniscal von Mises stress, maximum shear stress, and contact pressure across FPA conditions. Results: Tibiofemoral force increased during early stance (9–11%) in the toe-in condition with this increase reaching statistical significance in males (p = 0.008, mean partial η2=0.70 within the SPM-identified cluster). FE analysis showed that peak stresses and contact pressure were primarily localized in the anterior region of the medial meniscus. A consistent directional response to FPA was observed with the lowest peak values occurring in the toe-in condition and the highest values in the toe-out condition. Conclusion: Adjusting FPA modulates intra-articular knee loading via the kinetic chain. For FFF patients, neutral FPA provides stable loading. The toe-in condition presents a complex mechanism: despite increasing tibiofemoral force (notably in males), it reduces peak stress by altering contact mechanics and stress distribution. Therefore, FFF gait interventions must be individualized based on factors like foot morphology, sex, and functional goals.
Open Access: Yes
Optimizing landing mechanics to modulate patellar tendon loading: An individualized moment arm analysis
Publication Name: Iscience
Publication Date: 2026-05-15
Volume: 29
Issue: 5
Page Range: Unknown
Description:
Single-leg landing (SL) imposes substantial mechanical demand on the patellar tendon, with peak patellar tendon force (PPTF) serving as a key metric for characterizing the internal mechanical environment of the tendon. This study integrates 3D modeling with high-resolution in vivo kinematics to quantify the patellar tendon moment arm (PTMA) and the PPTF, examining their biomechanical correlations and neuromuscular features. Minimal sex-related PTMA differences suggest comparable anatomical leverage during knee flexion across both sexes. In both sexes, PPTF was significantly positively correlated with the knee flexion angle at initial contact (IC) and significantly negatively correlated with the knee range of motion (ROM). Muscle network analysis showed lower clustering coefficients in high-frequency versus low-frequency bands. Reduced IC knee flexion and increased ROM attenuate patellar tendon mechanical demand. By incorporating individualized moment-arm analysis, this study provides a biomechanical basis for understanding patellar tendon loading during landing.
Open Access: Yes
The effect of mixed fatigue on knee biomechanics and muscle activation during sidestep cutting in elite soccer players
Publication Name: BMC Sports Science Medicine and Rehabilitation
Publication Date: 2026-12-01
Volume: 18
Issue: 1
Page Range: Unknown
Description:
Background: Football is one of the most popular sports in the world, and it is also a sport with a high rate of injury. The study aims to investigate the effects of physical and mental mixed fatigue (PMF) on knee biomechanics during sidestep cutting maneuvers in elite male soccer players, thereby assessing the potential mechanisms underlying non-contact knee injuries. Methods: Thirty-six elite male soccer players were recruited (age: 21.61 ± 1.22 years; body mass: 75.16 ± 6.34 kg; height: 175.8 ± 3.53 cm; shoe size: 41–44 EUR). Following a targeted fatigue induction protocol, key lower limb biomechanical data were acquired during anticipated sidestep cutting maneuvers both pre- and post-PMF. Statistical analyses were performed utilizing paired sample t-tests and one-dimensional Statistical Parametric Mapping (SPM1d). Results: Following PMF, knee valgus increased at initial contact (P = 0.022). Kinetic analysis, supported by SPM1d, revealed a marked transition from an extensor-dominant to a flexor-dominant pattern in sagittal knee moments (P = 0.007), alongside elevated knee valgus moments (P = 0.039). Neuromuscularly, quadriceps and lateral gastrocnemius activation (iEMG/RMS) significantly decreased, whereas compensatory increases were observed in the hamstrings and medial gastrocnemius (all P < 0.001). Conclusion: While PMF preserved most kinematics, the statistically significant increase in knee valgus, though small in magnitude, suggests an impaired frontal-plane control that may elevate Anterior Cruciate Ligament (ACL) strain. The shift from quadriceps to hamstring dominance reflects a compensatory neuromuscular strategy. These findings emphasize the importance of incorporating cognitive load into injury-prevention programs and monitoring mental fatigue to reduce non-contact knee injury risks.
Open Access: Yes
